text: Molecular models of DNA structures are representations of the molecular geometry and topology of deoxyribonucleic acid (DNA) molecules using one of several means,  with the aim of simplifying and presenting the essential, physical and chemical, properties of DNA molecular structures either in vivo or in vitro.  These representations include closely packed spheres (CPK models) made of plastic, metal wires for skeletal models, graphic computations and animations by computers, artistic rendering.  Computer molecular models also allow animations and molecular dynamics simulations that are very important for understanding how DNA functions in vivo.
  The more advanced, computer-based molecular models of DNA involve molecular dynamics simulations and quantum mechanics computations of vibro-rotations, delocalized molecular orbitals (MOs), electric dipole moments, hydrogen-bonding, and so on.  DNA molecular dynamics modeling involves simulating deoxyribonucleic acid (DNA) molecular geometry and topology changes with time as a result of both intra- and inter- molecular interactions of DNA. Whereas molecular models of DNA molecules such as closely packed spheres (CPK models) made of plastic or metal wires for skeletal models are useful representations of static DNA structures, their usefulness is very limited for representing complex DNA dynamics. Computer molecular modeling allows both animations and molecular dynamics simulations that are very important to understand how DNA functions in vivo.